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Update qa/Dockerfile to be built from the project root context
See merge request gitlab-org/gitlab-ce!31533
(cherry picked from commit 4d4e88df)
6aa215aa Support X_if_ee methods for QA tests
b601cfcf Update qa/Dockerfile to be built from the project root context
9a4dcd8d Update the 'build-qa-image' job to be built from project root context